Hello to members of the Stata list. Thank you in advance for having a
look at this.

I have a six-column subject identifier coming into Stata from an ASCII
file that looks like the following:

B 1
B 120
CCH 7
CCH 23
CCH213
UW 23
UW 232

I want to read in and manipulate these 6 columns so that in the end, I
have a str6 variable that looks like this:

B001
B120
CCH007
CCH023
CCH213
UW023
UW232

That is, the first three columns have been right justified and the last
three columns have been left-padded with zeros. I have tried various
options, but so far, not much luck. I was considering reading them in
as six str1 variables and putting things together sort of by brute
force, but I thought I'd ask first. Any suggestions on good string
manipulations for this problem?